oba510 has commented on the following diary entries

I've tried to clean a lot of these up in the SF Bay Area and Boston. What I've observed is that in older parts of cities, they tend to be fairly well-known neighborhoods that can be easily re-tagged as place=neighbourhood or suburb, but the rest really need someone who is familiar with the area to fix them. Some are really obscure and wouldn't be fixable by someone from outside the immediate neighborhood.

For housing projects and trailer parks I've created a named landuse=residential polygon. Some of them are unincorporated communities that are big enough to be tagged as a village or town. A lot of them are old names for places that are already on the map, or names of towns that have been absorbed by other places and disappeared completely from modern use. A few of them were actually buildings. One of them was a trailhead. I've only seen one that actually was a hamlet.

In California many (maybe most) look like old names given to locations along railroad lines by the railroads in the 19th century, and those are harder to deal with. Some still exist in some form (usually towns, neighborhoods, or train stations), some were towns or stations that no longer exist, some only ever existed in theory.